Using the plasma decay data from the turnover of radiolabeled apolipoproteins A-I and A-II the residence times were determined in normals (4.7d, 5.1d), Tangier disease (.2d, 8d), abetalipoproteinemia (3.3d, 3.5d), Type I hyperlipoproteinemia (2.5d, 2.7d). These were compared to the turnover of high density lipoproteins and subfractions of HDL (HDL2, HDL3) in normal subjects with no significant difference. Compartmental models for A-I and A-II contain two plasma compartments, one decaying faster than the other. The fast decaying compartment was found to be increased in size and rate of decay: Tangier greater than Type I greater than abeta greater than normal thereby accounting for the decrease in A-I and A-II residence times. Triglyceride kinetics were studied in normals (greater than 125%, I.W.) and subjects with mild or marked obesity (greater than 160% I.W.). Using a compartmental model, the FRC' for VLDL-TG were compared. Synthesis rates were normal in the mildly obese group but increase in the markedly obese group. Estimates for the normal population were determined to be: TG synthesis 806 mg/hr, FCR .19/hr, TG residence time 5.16 hr. The triglyceride kinetics determined in Pima Indians were found to be qualitatively similar to the normals.